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Irrigation and oil accumulation (inolition): the two sides of the same coin

The diminution of rains and the raise in temperature present issues for the yield of oil from the fruit. There is still remedy

Summers are growing drier and drier. This affects olives, limiting their productivity.

It is well known that rains for 800 mm / year or more do not increase the productivity, but in many areas, the rain level is significantly lower. The irrigation can be recommended since it favors the number of fruits per tree and the productivity of the whole olive grove. It is not uncommon, during arid seasons, to record a 50% higher production from irrigated olive groves than from non-irrigated ones.

Rain waters not only increase the number of fruit per tree, but also have a beneficial effect on any single fruit.

Irrigation increases the total volume of the olive, of the stone and of the flesh. It also raises the flesh/stone ratio. These effects are obtained because the cellular size is larger, not because cells more actively reproduce.

An interesting effect occurs to the fruit when water stress is noticed in the weeks following the blossoming and ALLEGAGIONE. In this case, when a good watering status is restored after 4-9 weeks, the size of the stone is unaltered with respect to the irrigated fruits, whereas the pulp size is reduced. It is then concluded then, in order to obtain fruits of good size, irrigating the grove is instrumental, especially during summer months, such as July and August.

The inolition of the fruit is highest between September and October. The process of oil accumulation is normally considered as concluded by the beginning of October, but recent experiences demonstrated that it goes on during the following weeks in presence of mild temperatures and a good sun beam.

Therefore, irrigation is not only useful during the summer, but also during the fall, if rains are scarce.

Contrarily to the common belief, the yield of olives is increased, not diminished, in irrigated olive groves. The false belief of the contrary is due to the evidence that the yield in oil, expressed in percentage of fresh weight (calculated in the olive press) is lower. Still, the quantity of oil produced per tree or per hectare is considerably larger for irrigated areas than for dry areas.

As regards the ripening of the fruit, irrigation apparently delays, even though it seems that the quantity of olives carried by the tree is supposed to have a bigger influence on the phenomenon.

It can be concluded that irrigation directly affects the physiology of the olive tree and its fruits and that some of the induced consequences are still little known.



by T N
04 may 2009, Technical Area > Olive & Oil

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